This invention relates to heat exchangers that are formed from plate pairs in which an internal flow path through the plate pair is defined by cross-over ribs.
Heat exchangers are often formed from multiple plate pairs that are stacked and brazed, soldered, or mechanically or otherwise joined and sealed. In some applications, for example in refrigerant evaporator systems, heat exchangers are formed from stacked plate pairs that each define an internal U-shaped flow path for the refrigerant. In some plate pair heat exchangers outwardly projecting ribs provided on each of the plates of a plate pair cooperate to form the internal U-shaped flow path. In such a ribbed plate construction, the ribs on each plate are angled in a common direction, such that when two plates are arranged facing each other to form a plate pair, the internal groove provided by each rib on one plate crosses-over a number of the internal grooves provided by ribs on the facing plate, thereby forming the internal flow path. Typically, at the U-turn portion of the flow path, the angled ribs are longer in order to pass the fluid around the U-turn. Examples of cross-over rib heat exchangers can be seen in U.S. Pat. No. 3,258,832 issued Jul. 5, 1966 and U.S. Pat. No. 4,249,597 issued Feb. 10, 1981.
In conventional designs for U-shaped flow path cross-over rib heat exchangers, the internal fluid is subjected to a relatively large pressure drop at the turn-around portion of a plate pair flow path, relative to the total drop across the rest of the plate pair. Additionally, in conventional designs, the internal fluid is not always directed around the turn-around portion in the most efficient manner for promoting heat exchange. For example, fluid entering the turn-around zone may have different phase characteristics based on a relative location of the fluid within the internal flow path. In conventional cross-rib plate designs, fluid passing around the turn-around portion is indiscriminately mixed without regard for such differing characteristics. Thus, there is a need for a cross-rib type plate pair heat exchanger in which the pressure drop in transferring fluid around the turn-around portion is minimized and fluid is routed around the turn-around portion in a pattern that increases heat exchanger efficiency.